By Linda P. Case

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Keep those Doggies Rollin’……Rawhide, Rawhide!

I have always hoped that someday I would find a connection between the Blues Brothers and dog nutrition. That day has come.

Rawhide, Rawhide: A dog person cannot walk into a pet supply store (or their own grocery store, for that matter) without noticing the explosion in the number of dog chews, dental devices and edible bones that are available for sale today. Some of these are biscuit or extruded concoctions containing a mixture of ingredients, while others originate from cow skin (rawhide chews) or are the left-over body parts of a hapless food animal (pig/lamb ears, hooves, and bully sticks).

If you do not know what a bully stick is, ask your mother. Better yet, ask your father.

Even as the selection of these items has expanded, nutritional information about them is still glaringly absent. Since all of these products are intended to be chewed slowly so that pieces or the entire product will be gradually consumed by the dog, we should at least be informed as to whether these items are actually digested by dogs, should we not?

Are they digestible? Dry matter digestibility refers to the proportion of a food that a dog’s gastrointestinal tract is capable of breaking down (digesting) and absorbing into the body. When we talk about the digestibility of a dog food, we are primarily concerned with its nutrient value and ability to nourish the dog. However, when we are considering the digestibility of rawhide treats, chews and dental products, the concerns are different but equally important. Any portion of a chew that is broken off and swallowed will travel through the length of a dog’s gastrointestinal tract, just like any other food. And, if the dog is able to bite off large chunks or swallow an entire chew at once, that piece has the potential to cause digestive upset, impede normal gut motility, or in the worse case scenario, cause obstruction if it is not dissolved and digested as it moves along.

Recently, a team of researchers at the University of Illinois decided to examine exactly this question by comparing the digestibility of different types of dog chews.

The studies: Two studies were conducted, both using an in vitro (test tube) technique that has been validated as a measure of the digestive conditions that occur in a dog’s stomach (gastric digestion) and small intestine (intestinal digestion). The first study compared in vitro dry matter digestibilities of sample products from six broad categories of dog treats (1). All of the products that were tested were produced by Hartz Mountain Corporation and the study was funded by the company. The second study compared just two types of treats, pork skin versus beef rawhide chews (2). The researchers also measured digestibility of the pork skin chew using a feeding trial with dogs. (For an explanation of digestibility trials with dogs, see Scoopin’ for Science). The reason for not doing a feeding study with the beef rawhide chew was not explained in the paper.

Results: Together, the two studies reported several interesting differences between the digestibility of dog chews:

Chews made from pig’s ears, which are composed primarily of cartilage and the protein collagen had very low gastric (stomach) digestibilities (14 %). Although these were almost completely digested in the intestinal environment (90 %), the lack of change in gastric acid means that a pig’s ear treat, if swallowed, would potentially leave the stomach intact and enter the small intestine will little change in size and consistency.

Similarly, with the exception of one product, rawhide chews made from cow skin were very poorly digested in the stomach. Intestinal digestion was almost complete for one product, but others continued to have low digestibility, even in the intestinal environment. The researchers noted that feeding rawhide chews to a dog who tended to consume large pieces could increase a dog’s risk for intestinal blockage.

When a pork skin chew was compared directly to a beef rawhide chew, the pork skin product’s digestibility was significantly greater than that of beef rawhide chew. After six hours, which is approximately the time it takes for a meal to begin to leave a dog’s stomach and enter the small intestine, the pork chew was more than 50 percent digested, while the rawhide was only 7.6 percent digested. This low rate of gastric break down continued even when tested up to 24 hours. After simulation of digestion in the small intestine (the major site of digestive processes in dogs), the pork skin rawhide was almost 100 % digested, while the beef rawhide reached only 50 to 70 % digestion under the same conditions. Rawhide was digested up to 85 % only when exposed to the intestinal conditions for 24 hours.

When dogs were fed one pork skin chew per day along with their normal diet, the overall digestibility of the diet increased. This corroborates the in vitro results and supports the conclusion that the pork skin chews were highly digestible.

Take Away for Dog Folks:

One of the most interesting results of these studies was the finding of such a large difference between the digestibility of pork skin versus beef rawhide chews. Because some dogs consume these types of chews rapidly and swallow large chunks, the fact that pork chews but not beef rawhides are highly degraded in the stomach and are highly digestible overall, is of significance to dog owners. These data suggest that if an owner is going to feed some type of rawhide chew (and mind you, I am not advocating for feeding these types of treats), but if one was choosing and had a dog who might consume the treat rapidly, feeding a pork skin chew appears to be a safer bet than a beef rawhide chew.

Second, it is important to note that all types of rawhide-type chews are composed of collagen, a structural protein that makes up most of the connective tissues in the body. This is true for ears, pig skin, rawhide, and yes, even bully sticks. As these data show, collagen can be highly digestible (or not). The difference most likely depends on the source of the product and the type of processing that is used, both of which vary a great deal among products.

Feeding dog a chew that is composed of collagen, even when it is highly digestible collagen, does not a nutritious treat make. Although collagen is a very important and essential protein in the body, it is not a highly nutritious food protein because it is composed almost completely of non-essential amino acids and is deficient in four of the essential amino acids. What this means from a practical perspective is that even though certain types of rawhide chews are found to be highly digestible and safe (from a digestibility perspective), this does not mean that they are providing high quality nutrition to the dog. In fact, they do not. While this research is important for pushing the peanut forward regarding the safety of these products in terms of digestibility, effects on gut motility, and risk of blockage, we still need more information (and selection) of chews for dogs that are both digestible and nutritious.

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41 thoughts on “Keep those Doggies Rollin’……Rawhide, Rawhide!”

Linda, as always a great post. I recently came across a paper that suggested non-digestible structural protein like the ones you mentioned may promote the growth of non-beneficial colonic bacteria that contributes to gas production, bloating, farting and even diarrhea.

Hi Ken – Thanks, and nice to hear from you! If you have a PDF of the paper that you mention, I would love to have a copy. It might make a good blog piece. Just send it to my private email, if you have it. Hope all is well with you! Linda

Thank you for shedding more light on this. Nutrition aside, I think many people look to these products as more something that satisfies the dog’s chewing desire, and is more easily replaceable then wooden table legs and such. While they enjoy pig ears and the like, those are consumed too quickly, while bully sticks and especially rawhide last much longer. Years ago my dog loved rawhide, until he swallowed too large a piece and choked. Fortunately, I caught it immediately and knew what to do, ending up with only a mess on the floor. But that was his last rawhide. There are now rawhide-free chew bones (e.g. SmartBones) with vegetable on the outside and chicken inside. The ingredients look okay, but I’d be interested if you had any opinion on them.

And, they just don’t last nearly as long as rawhide. In that respect, the bully sticks appear much safer, and do last awhile with many dogs, and seem to be the best choice for keeping him busy.

Yes, he does have bones, but they seem less appealing for long chews. I even have something I think they called a compressed bone, that was supposed to last a long time. But I needed a bandsaw to cut it down, and nothing less than an American Bulldog was able to even make a dent in it! But it certainly does last, for years…

Hi Gerry, Thanks for your comment. I completely agree that the need to chew (and to chew on appropriate things!) is an important issue here. Personally, we have searched for years to find chew bones/toys that our dogs enjoy and use, yet are still safe. For a while we used the white sterilized bones, until we saw reports of (and experienced) slab fractures to our dogs molars and pre-molars. Like you, we too had a very bad experience with a dog swallowing a large chunk of a rawhide, many years ago. Nyla bones work (kind of), but I am not thrilled with using plastic for chew toys. One of our current favorites are various types of Kongs, stuffed with high quality soft treats (which there are a nice selection of these days…..looking for a research paper that compares those!). I know all dedicated dog folks struggle with this issue, so was happy to see Maria’ and Kelly’s group’s study on treats. Let’s hope we see some more like this soon! Best, Linda

Many like the chewable Nyla bones, but they don’t last very long at all. The original ones do last, but aren’t as attractive to dogs, not even after sitting in hot broth for awhile. The plastic there doesn’t concern me, as the pieces and quantity remain very small. One dog loves his Kong, but knows how to empty it quickly unless frozen, and that leaves a mess unless it’s in a crate, which he isn’t. So that mainly leaves an occasional bully stick.

It seems as though nearly everthing has it’s warnings, even Greenies, and there are few places you can trust on opinions, other than you and snopes.com. About the only thing I’ve found that’s safe to chew on and really lasts, was to get him a brother and sister.

Hi “Dorannadurgin” – In the digestibility trial, the dogs were fed a commercial, adult maintenance dry (kibble) food. As far as the in vitro test environment, the conditions were set up to simulate the gastric secretions and pH of a typical dog’s stomach and then similarly, those of the small intestine. (A reference to the paper that developed and validated the tool is included in the full text of the publications, fyi). To my knowledge, there are no studies that demonstrate consistent differences in the intestinal environment of kibble-fed versus raw-fed diets. (This does not mean such differences do not exist, just that I have not seen papers [yet] that demonstrate and support claims of such a difference). Linda Case

I have been reading a lot lately about the effect of diet on gut bacteria, and therefore on the overall health of the individual.
I wonder how “dry kibble’ affects the gut bacteria, and therefore how worthwhile studies are done on the digestibility of “chews” using ONLY kibble fed dogs!
I know absolutely that my dogs do very poorly on ANY Commercial dry dog foods. They get smelly, gassy diarrhoea immediately and after any period with dry food, their coats become harsh and smelly.
Could it be that dogs fed on a mostly Commercial Dry Dog food, and gut bacteria that cannot aid the digestion of bone, gristle or skin?

I have become very wary of raw hide recently, hearing stories of how they can splinter and puncture a dog internally. I have shied away from raw hide lately, leaning more towards Kong & Nylabone chew toys, the ones that are textured vs. smooth and either stuffable or flavored. I really just need something to give my dogs that they can chew that will last awhile. Thanks for this informative post!

Hi Cathy – I agree that it is so difficult to find appropriate chew toys for our dogs that they enjoy and that we trust to be safe. I am glad we are starting to see research such as these studies to give us a bit of guidance. Thanks for reading and for your comment! Linda

I have fed my dogs on “cows legs, from a local Station (aka “Ranch”) They got hhoofs as well as the entire skin, hair and all. When they were finished there was nothing left but a piece of hoof. Their ‘droppings’ consisted a of just about nothing by cow hair! (not to mention that that year, they were beautifully healthy!! 🙂
When we returned to the city, I could no longer get such ‘luxuries’ for my dogs, but feed, when I can get them, fresh pigs trotters in addition to their normal dinners. There appears to be no residue from the trotters — no bone, no skin and no cartilage.

I suspect that what’s ok to chew depends a lot on the individual. My dogs (I bred Labs on a small scale for a decade and have a few dozen Labs over the last 20 years) seem to have cast iron digestive tracts, and nothing they’ve ingested has resulted in a vet visit. They’ve tried a wide range of chews, including table legs, big bones, little bones, rawhide, wood (probably flavored by various sorts of fungal decay) and misc. unmentionables. Even puking is rare. All my furniture is second hand junk so I don’t get upset when they chew.
The problem with a lot of the ‘science’ studies is that they are reductionist in nature. I wish we had more studies dealing with the ‘big question’ sort of science. Eg., the big questions here are (1) how important is chewing on stuff, and how does it vary between dogs’ (2) if there is a need to chew, what are the best things to satisfy that need? How does the ‘optimal chew’ vary with age, breed, etc. (3) is chewing good for dental hygine?

Jen – I think you are confusing “controlled” with “reductionist”. There is nothing at all that is reductionist about the studies that are summarized here. These are about as applied as a research study can get – the investigators looked at the ability of gastric secretions and intestinal enzymes from dogs to break down chews that are routinely fed to dogs. They followed this with a study that tested this ability directly with dogs. Regarding your comment about dental health and chewing – there actually are studies of the relationship between chewing (and the abrasion that it provides to tooth surfaces) and dental health. We now know for example that providing opportunities for regular and prolonged chewing, plus regular tooth brushing, are key to dental health in dogs. This information came from the practice of controlled scientific studies, not anecdotal stories. Similarly, behaviorist and cognitive scientists ARE studying many basic behavioral needs of dogs, such as chewing, sniffing, breed differences in behavior, etc. through the use of both well controlled lab studies and using studies of dogs living in homes. There is a great deal of good science taking place for dogs today, providing loads of information that can help us to care for and understand our dogs better. Linda Case

Your welcome, great and informative article. I stopped feeding rawhide bones chews etc a long time ago. More often than not I ended up with my hand down my dogs throats trying to retrieve the broken off knots, to prevent them from choking.

Hi Laura, I would be interested in your thoughts on whether the composition of beef hide products from Wholesome Hide differ significantly from other beef hide products on the market, in terms of safety for the dog.

Hi “Alaska”, The studies did examine several brands of rawhide chews and although the beef rawhides were generally less digestible than pig skin chews, they did report variability in gastric digestibility among the rawhide products. For example, one product was degraded ~ 70 % in the gastric phase. However, unfortunately the studies did not identify specific brands, so we cannot know what was different about that particular brand. It is likely that the variability that is seen within the types of products that were examine and among the various categories is affected by original source of materials and the type of processing used. Thanks for reading and for your comment! Linda Case

Thanks for your reply. It made me go back and read the blog post again, as well as the other comments, and now I am wondering why you feel that chews need to be nutritious? It seems to me that digestibility is important, as is safety of ingredients, but if the main reason for giving chews to dogs is for the distraction value (and possibly the dental value), why care about the nutritive value?

Also, thanks for not censoring my initial question because I mentioned a specific brand. I realized afterwards that it could be considered a spam comment but I have no connection with the company. It is just that WH is the only source of beef hide products I know of that does not use preservatives or chemicals (other than dilute hydrogen peroxide) in processing. That seems significant to me and I was wondering if there was any science regarding the safety (or lack thereof) of the chemicals typically used for processing beef hide into dog chews.

I am always looking for better thing for my Lab to chew on. She is a VERY determined chewer with a sensitive stomach. I got her a black Kong and she was managing to get quarter-sized chunks off within 15 minutes. Even a black Kong ball (the correct size or the next size up) only lasted a week or so before she was ripping pieces off of it.
She has only had 1 bully stick, and after about 5 minutes of chewing on it, she had diarrhea for about 24 hours. So, I tend to stay away from most of the digestible chews.
Elk antlers last and she enjoys them, but I do worry about the risk of fracture to her teeth.
The only thing we have found that seems to be safe for her teeth and stomach, and that she cannot destroy quickly is a Goughnut. She has had that for about a year now and it still looks almost brand new. She does like it, but it doesn’t seem to satisfy her need to chew the way the antlers do.
Any other suggestions?

Hi Ann, Nice to hear from you! I hope all is well with you! I agree that it is a very tough thing, as all of our dogs need and love to chew, but we want to find chew toys that are safe and are of high quality. I have heard good things about Goughnuts, but have not tried them. We have had student who use the Nylabone “Galileo” that is designed for hard chewers (and boy, it is tough), but then of course you have the problem with consumption which can be a problem with plastic toys. For our dogs, we use Nylabones as our dogs only very gradually get very small bits off of them (none of our current dogs are tough chewers). The thing that we use most often currently are various Kongs that we stuff with high quality soft treats. Those (for now anyway) work well for both chewing and as safety cues for our dogs when they are home alone. I imagine for your girl that Kong would not be tough enough material though……

My dog loves bully sticks and he gets them regularly but they don’t last too long – maybe half an hour. The only truly long-lasting chew I have discovered that he retains an interest in are the Himalayan chews. Any thoughts on that? I just have to watch him to make sure to take them away once he whittles them down to a small chunk because he once swallowed it without my noticing and hours later puked it up.

Hi Jasper’s Mom – One of our training students had one of the Himalayan chews with her at class a few weeks ago. I had never seen these before – they are really interesting, as they are presumably made from, wait for it……Yak Milk. (It sounds like something out of a Monty Python skit, doesn’t it?). Anyway, joke potential aside, she had these for her two Standard Poodles, who are both moderate level chewers and she said that they loved them and it took them a couple of weeks to go through one. I don’t think they would work for really vigorous chewers, but am definitely going to look into these. I have not seen any studies of them yet, but would hypothesize that they are digestible, seeing that they are made from a dairy product. (That said, you would probably want to not use these with a dog who could consume them rapidly). Thanks for posting – I will keep my eyes open for a study of these!

My vet says no rawhide. He also said the he’s done too many surgeries to remove blockages from rawhide and ears, etc. And that while he makes money off these surgeries he in good conscience warns against them. Love my vet.

I’m confused about the results. In point 1 you say “a pig’s ear treat, if swallowed, would potentially leave the stomach intact and enter the small intestine will little change in size and consistency” but point 3 says “After six hours, which is approximately the time it takes for a meal to begin to leave a dog’s stomach and enter the small intestine, the pork chew was more than 50 percent digested.”

Wouldn’t point 3 mean that the pig’s ear was getting significantly digested in the stomach, and should be roughly half as large as it was when swallowed?

I no longer give my dogs rawhide due to the negative things I’ve read about them and I already wasn’t keen on them. When they need to be distracted or kept busy (they both have a bit of separation anxiety ) they get bully sticks. My 30-lb. senior girl takes about 3-4 hrs. to finish a normal size stick but I usually can save half for later. My 50-lb. middle-aged girl takes about 30-45 mins. with a giant stick. Occasionally they will get a Kong which lasts a pretty good while for both of them. I don’t like to give treats on a regular basis due to efforts to prevent weight gain. I find the older they get the more obsessed they become with food so I limit what they eat between meals, which is the occasional chew. Thanks for this informative post. And also thanks to the readers for their suggestions on other things I can try.